1. Technical Field
This application relates to a rotary cutting tool, especially a drilling tool, composed of a tool shank and an exchangeable cutting insert. The tool shank, on its circumference, is provided with a limb with a bearing surface bordering on the circumference of the tool shank and inclined relative to the tool axis and corresponding to a likewise inclined bearing surface on a wing of the cutting insert. The orientation of the inclination of the bearing surfaces corresponds to the direction of rotation of the tool, and the cutting insert only partly covers the tip of the tool shank.
2. Background Information
A drilling tool comprising an exchangeable cutting insert is known from EP 0 118 806 B1, for example. Said drilling tool may have a tool shank with an accommodation for inserting a fastening pin of the cutting insert. When the cutting insert is inserted, it may be rotated by an angle of approx. 45° relative to the tool shank. No other fastening element may be provided. The cutting insert and the tool body could be configured such that the shank-end narrow side of the cutting plate may be braced against the shank-end rim of the recess in the tool shank. An axial force between the tool shank and the cutting insert can be produced in that the shank-end rim of the recess may rise slightly in the direction of insertion. The fastening pin can be secured against being pulled out of the tool shank by means of a shank-end widening. This may cause bracing when the cutting insert is rotated into the seat, which may be intensified by cutting at higher cutting forces. The axial force generated by such bracing may pull the cutting insert away from the tool body. The stability of the mount of the cutting insert on the tool shank and the mechanical load capacity of the drilling tool overall may be restricted thereby.
According to another embodiment of the cutting tool known from EP 0 118 806 B1, the fastening pin may be disposed concentrically on the cutting insert and may be provided with bearing surfaces rising slightly twisting in the direction of the cutting rotation. By said slightly twisting configuration of the bearing surfaces on the fastening pin, which can be in contact with correspondingly formed bearing surfaces on the seat for the tool shank, an axial force may be applied on the cutting insert in the direction toward the tool body. Said axial force may act fully on the fastening pin, which may be small in size compared to the tool diameter and thus may have a low mechanical load capacity.
Additionally, a torque may be applied to the fastening pin, which may further reduce the mechanical load capacity of the connection between the tool shank and the cutting insert.